AS Wales endures its harshest winter in 30 years, bird groups are anxious to discover the impact on our feathered friends.

Both RSPB Cymru and the British Trust for Ornithology are keen to know how the wintry conditions are affecting garden bird numbers and whether people have seen any unusual visitors.

The RSPB said that, during this month’s cold snap, its switchboards and website were inundated with people looking for advice on feeding hungry garden birds.

And Geoff Gibbs, one of Wales’ top bird recorders, said his garden in Llanfairfechan had become a refuge for all sorts of bird species.

“We normally see about seven or eight species in a week, not counting birds flying over,” said Geoff, the BTO assistant Wales officer.

“In just a few days we saw 17 species, including our first-ever brambling and birds like starling and carrion crow, which are unusual visitors to our garden.”

This weekend sees the RSPCA’s annual Big Garden Birdwatch, when bird lovers join together to provide a snapshot of the country’s bird populations.

Last year a record-breaking 33,000 people in Wales took part in the survey.

Dana Thomas, of RSPB Cymru, said this year’s survey will help improve understanding of the effects of the prolonged cold weather.

She said: “We can expect to see some more unusual species, particularly redwings, fieldfares and tree sparrows that are struggling to find food elsewhere.”

The harsh weather is particularly bad for birds with small bodies like robins, long tailed-tits and wrens.

Dana added: “Sadly, we may even see the robin fall out of the top 10 for the first time since the start of the survey 31 years ago.”

Taking part in the Big Garden Birdwatch requires just one hour on Saturday or Sunday – and can be done from the comfort of your living room.

In contrast the BTO carries out a year-round garden watch, which provided telling insights during the heavy snowfall that affected parts of Britain in February 2009.

It showed that ground-feeding species, such as chaffinch, peaked in gardens as they utilised food scraps.

Dr Tim Harrison, of the BTO, said: “Winter feeding has been shown to increase survival rates of many different species of birds. With blue tits, such feeding can even have a positive influence on breeding success in the following spring.”

Big Garden Birdwatch events are also taking place around Wales this weekend, offering tips and advice on how to care for garden birds. Visit www.rspb.org.uk/birdwatch for details.

RSPB Conwy is hosting a Big Reserve Birdwatch (10am-4pm both days). The event is free, but there is an entry charge for non-members. Details: 01492 584091.

At Loggerheads Country Park, near Mold, there’s a bird count (10.30am- 3.30pm both days). Visitors can also pick up bird care tips from RSPB staff. Des James, 07849 038939.

RSPB Ynys-hir, near Machynlleth, is also doing its bit. Visitors can brush up on their bird ID skills and take part in bird quizzes (10am-4pm both days).Details: 01654 700022.

For a free guide on feeding garden birds or to join the BTO Garden BirdWatch, call 01842 750050.